Re: [PATCH 1/4] libsepol/cil: Provide option to allow qualified names in declarations

[James Carter <jwcart2@gmail.com>]

On Thu, Jun 24, 2021 at 4:21 PM Dominick Grift
<dominick.grift@defensec.nl> wrote:
>
> James Carter <jwcart2@gmail.com> writes:
>
> > Qualified names have "dots" in them. They are generated when a CIL
> > policy is compiled and come from declarations in blocks. If a kernel
> > policy is decompiled into a CIL policy, the resulting policy could
> > have decarations that use qualified names. Compiling this policy would
> > result in an error because "dots" in declarations are not allowed.
> >
> > Qualified names in a policy are normally used to refer to the name of
> > identifiers, blocks, macros, or optionals that are declared in a
> > different block (that is not a parent). Name resolution is based on
> > splitting a name based on the "dots", searching the parents up to the
> > global namespace for the first block using the first part of the name,
> > using the second part of the name to lookup the next block using the
> > first block's symbol tables, looking up the third block in the second's
> > symbol tables, and so on.
> >
> > To allow the option of using qualified names in declarations:
> >
> > 1) Create a field in the struct cil_db called "qualified_names" which
> > is set to CIL_TRUE when qualified names are to be used. This field is
> > checked in cil_verify_name() and "dots" are allowed if qualified names
> > are being allowed.
> >
> > 2) Only allow the direct lookup of the whole name in the global symbol
> > table. This means that blocks, blockinherits, blockabstracts, and in-
> > statements cannot be allowed. Use the "qualified_names" field of the
> > cil_db to know when using one of these should result in an error.
> >
> > 3) Create the function cil_set_qualified_names() that is used to set
> > the "qualified_names" field. Export the function in libsepol.
>
> I wonder what the use-case for this functionality is?
>

Compiling a kernel policy that has been turned back into CIL.

Having something like
  (block b
     (type t)
      ....
  )
will result in the type "b.t" in the kernel policy and "b.t" is not
valid in a declaration.

Of course, you can turn the kernel policy into a policy.conf and
compile it with checkpolicy, but I would like to be able to compile it
with secilc.

Another use case is with secil2tree. This generates valid CIL if you
use "-A build", but not if you use "-A resolve". One reason the policy
is not valid is that the names are qualified at this point and will
have "dots" in them if there are declarations within blocks in the
policy. (Another reason the resulting policy would not be valid is
that there are still blocks in it even though they have been
essentially "resolved".)

Jim


> >
> > Signed-off-by: James Carter <jwcart2@gmail.com>
> > ---
> >  libsepol/cil/include/cil/cil.h     |  1 +
> >  libsepol/cil/src/cil.c             |  6 ++++++
> >  libsepol/cil/src/cil_build_ast.c   | 24 ++++++++++++++++++++++--
> >  libsepol/cil/src/cil_internal.h    |  1 +
> >  libsepol/cil/src/cil_resolve_ast.c |  4 ++--
> >  libsepol/cil/src/cil_verify.c      | 19 ++++++++++++++-----
> >  libsepol/cil/src/cil_verify.h      |  2 +-
> >  libsepol/src/libsepol.map.in       |  1 +
> >  8 files changed, 48 insertions(+), 10 deletions(-)
> >
> > diff --git a/libsepol/cil/include/cil/cil.h b/libsepol/cil/include/cil/cil.h
> > index 92fac6e1..482ca522 100644
> > --- a/libsepol/cil/include/cil/cil.h
> > +++ b/libsepol/cil/include/cil/cil.h
> > @@ -51,6 +51,7 @@ extern int cil_selinuxusers_to_string(cil_db_t *db, char **out, size_t *size);
> >  extern int cil_filecons_to_string(cil_db_t *db, char **out, size_t *size);
> >  extern void cil_set_disable_dontaudit(cil_db_t *db, int disable_dontaudit);
> >  extern void cil_set_multiple_decls(cil_db_t *db, int multiple_decls);
> > +extern void cil_set_qualified_names(struct cil_db *db, int qualified_names);
> >  extern void cil_set_disable_neverallow(cil_db_t *db, int disable_neverallow);
> >  extern void cil_set_preserve_tunables(cil_db_t *db, int preserve_tunables);
> >  extern int cil_set_handle_unknown(cil_db_t *db, int handle_unknown);
> > diff --git a/libsepol/cil/src/cil.c b/libsepol/cil/src/cil.c
> > index 9d5038d9..3f2e6927 100644
> > --- a/libsepol/cil/src/cil.c
> > +++ b/libsepol/cil/src/cil.c
> > @@ -440,6 +440,7 @@ void cil_db_init(struct cil_db **db)
> >       (*db)->handle_unknown = -1;
> >       (*db)->mls = -1;
> >       (*db)->multiple_decls = CIL_FALSE;
> > +     (*db)->qualified_names = CIL_FALSE;
> >       (*db)->target_platform = SEPOL_TARGET_SELINUX;
> >       (*db)->policy_version = POLICYDB_VERSION_MAX;
> >  }
> > @@ -1872,6 +1873,11 @@ void cil_set_multiple_decls(struct cil_db *db, int multiple_decls)
> >       db->multiple_decls = multiple_decls;
> >  }
> >
> > +void cil_set_qualified_names(struct cil_db *db, int qualified_names)
> > +{
> > +     db->qualified_names = qualified_names;
> > +}
> > +
> >  void cil_set_target_platform(struct cil_db *db, int target_platform)
> >  {
> >       db->target_platform = target_platform;
> > diff --git a/libsepol/cil/src/cil_build_ast.c b/libsepol/cil/src/cil_build_ast.c
> > index baed3e58..9da90883 100644
> > --- a/libsepol/cil/src/cil_build_ast.c
> > +++ b/libsepol/cil/src/cil_build_ast.c
> > @@ -146,7 +146,7 @@ int cil_gen_node(struct cil_db *db, struct cil_tree_node *ast_node, struct cil_s
> >       int rc = SEPOL_ERR;
> >       symtab_t *symtab = NULL;
> >
> > -     rc = cil_verify_name((const char*)key, nflavor);
> > +     rc = cil_verify_name(db, (const char*)key, nflavor);
> >       if (rc != SEPOL_OK) {
> >               goto exit;
> >       }
> > @@ -204,6 +204,11 @@ int cil_gen_block(struct cil_db *db, struct cil_tree_node *parse_current, struct
> >               goto exit;
> >       }
> >
> > +     if (db->qualified_names) {
> > +             cil_log(CIL_ERR, "Blocks are not allowed when the option for qualified names is used\n");
> > +             goto exit;
> > +     }
> > +
> >       rc = __cil_verify_syntax(parse_current, syntax, syntax_len);
> >       if (rc != SEPOL_OK) {
> >               goto exit;
> > @@ -274,6 +279,11 @@ int cil_gen_blockinherit(struct cil_db *db, struct cil_tree_node *parse_current,
> >               goto exit;
> >       }
> >
> > +     if (db->qualified_names) {
> > +             cil_log(CIL_ERR, "Block inherit rules are not allowed when the option for qualified names is used\n");
> > +             goto exit;
> > +     }
> > +
> >       rc = __cil_verify_syntax(parse_current, syntax, syntax_len);
> >       if (rc != SEPOL_OK) {
> >               goto exit;
> > @@ -331,6 +341,11 @@ int cil_gen_blockabstract(struct cil_db *db, struct cil_tree_node *parse_current
> >               goto exit;
> >       }
> >
> > +     if (db->qualified_names) {
> > +             cil_log(CIL_ERR, "Block abstract rules are not allowed when the option for qualified names is used\n");
> > +             goto exit;
> > +     }
> > +
> >       rc = __cil_verify_syntax(parse_current, syntax, syntax_len);
> >       if (rc != SEPOL_OK) {
> >               goto exit;
> > @@ -376,6 +391,11 @@ int cil_gen_in(struct cil_db *db, struct cil_tree_node *parse_current, struct ci
> >               goto exit;
> >       }
> >
> > +     if (db->qualified_names) {
> > +             cil_log(CIL_ERR, "In-statements are not allowed when the option for qualified names is used\n");
> > +             goto exit;
> > +     }
> > +
> >       rc = __cil_verify_syntax(parse_current, syntax, syntax_len);
> >       if (rc != SEPOL_OK) {
> >               goto exit;
> > @@ -5261,7 +5281,7 @@ int cil_gen_macro(struct cil_db *db, struct cil_tree_node *parse_current, struct
> >
> >               param->str =  current_item->cl_head->next->data;
> >
> > -             rc = cil_verify_name(param->str, param->flavor);
> > +             rc = cil_verify_name(db, param->str, param->flavor);
> >               if (rc != SEPOL_OK) {
> >                       cil_destroy_param(param);
> >                       goto exit;
> > diff --git a/libsepol/cil/src/cil_internal.h b/libsepol/cil/src/cil_internal.h
> > index 8b9aeabf..f184d739 100644
> > --- a/libsepol/cil/src/cil_internal.h
> > +++ b/libsepol/cil/src/cil_internal.h
> > @@ -321,6 +321,7 @@ struct cil_db {
> >       int handle_unknown;
> >       int mls;
> >       int multiple_decls;
> > +     int qualified_names;
> >       int target_platform;
> >       int policy_version;
> >  };
> > diff --git a/libsepol/cil/src/cil_resolve_ast.c b/libsepol/cil/src/cil_resolve_ast.c
> > index 5245cc15..27efffa6 100644
> > --- a/libsepol/cil/src/cil_resolve_ast.c
> > +++ b/libsepol/cil/src/cil_resolve_ast.c
> > @@ -4409,8 +4409,8 @@ int cil_resolve_name_keep_aliases(struct cil_tree_node *ast_node, char *name, en
> >
> >       *datum = NULL;
> >
> > -     if (strchr(name,'.') == NULL) {
> > -             /* No '.' in name */
> > +     if (db->qualified_names || strchr(name,'.') == NULL) {
> > +             /* Using qualified names or No '.' in name */
> >               rc = __cil_resolve_name_helper(db, ast_node->parent, name, sym_index, datum);
> >               if (rc != SEPOL_OK) {
> >                       goto exit;
> > diff --git a/libsepol/cil/src/cil_verify.c b/libsepol/cil/src/cil_verify.c
> > index 59397f70..9cb1a6f6 100644
> > --- a/libsepol/cil/src/cil_verify.c
> > +++ b/libsepol/cil/src/cil_verify.c
> > @@ -92,7 +92,7 @@ static int __cil_is_reserved_name(const char *name, enum cil_flavor flavor)
> >       return CIL_FALSE;
> >  }
> >
> > -int cil_verify_name(const char *name, enum cil_flavor flavor)
> > +int cil_verify_name(struct cil_db *db, const char *name, enum cil_flavor flavor)
> >  {
> >       int rc = SEPOL_ERR;
> >       int len;
> > @@ -116,10 +116,19 @@ int cil_verify_name(const char *name, enum cil_flavor flavor)
> >                       goto exit;
> >       }
> >
> > -     for (i = 1; i < len; i++) {
> > -             if (!isalnum(name[i]) && name[i] != '_' && name[i] != '-') {
> > -                     cil_log(CIL_ERR, "Invalid character \"%c\" in %s\n", name[i], name);
> > -                     goto exit;
> > +     if (db->qualified_names == CIL_FALSE) {
> > +             for (i = 1; i < len; i++) {
> > +                     if (!isalnum(name[i]) && name[i] != '_' && name[i] != '-') {
> > +                             cil_log(CIL_ERR, "Invalid character \"%c\" in %s\n", name[i], name);
> > +                             goto exit;
> > +                     }
> > +             }
> > +     } else {
> > +             for (i = 1; i < len; i++) {
> > +                     if (!isalnum(name[i]) && name[i] != '_' && name[i] != '-' && name[i] != '.') {
> > +                             cil_log(CIL_ERR, "Invalid character \"%c\" in %s\n", name[i], name);
> > +                             goto exit;
> > +                     }
> >               }
> >       }
> >
> > diff --git a/libsepol/cil/src/cil_verify.h b/libsepol/cil/src/cil_verify.h
> > index 4ea14f5b..8eb3c463 100644
> > --- a/libsepol/cil/src/cil_verify.h
> > +++ b/libsepol/cil/src/cil_verify.h
> > @@ -56,7 +56,7 @@ struct cil_args_verify {
> >       int *pass;
> >  };
> >
> > -int cil_verify_name(const char *name, enum cil_flavor flavor);
> > +int cil_verify_name(struct cil_db *db, const char *name, enum cil_flavor flavor);
> >  int __cil_verify_syntax(struct cil_tree_node *parse_current, enum cil_syntax s[], int len);
> >  int cil_verify_expr_syntax(struct cil_tree_node *current, enum cil_flavor op, enum cil_flavor expr_flavor);
> >  int cil_verify_constraint_leaf_expr_syntax(enum cil_flavor l_flavor, enum cil_flavor r_flavor, enum cil_flavor op, enum cil_flavor expr_flavor);
> > diff --git a/libsepol/src/libsepol.map.in b/libsepol/src/libsepol.map.in
> > index 2e503bd1..0e05d606 100644
> > --- a/libsepol/src/libsepol.map.in
> > +++ b/libsepol/src/libsepol.map.in
> > @@ -272,4 +272,5 @@ LIBSEPOL_3.0 {
> >       cil_write_parse_ast;
> >       cil_write_build_ast;
> >       cil_write_resolve_ast;
> > +     cil_set_qualified_names;
> >  } LIBSEPOL_1.1;
>
> --
> gpg --locate-keys dominick.grift@defensec.nl
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> Dominick Grift